The present invention relates to freight-carrying railroad cars of the type known as center beam or center partition bulkhead flat cars, and in particular relates a center beam for a center beam car providing enhanced protection for the car's cargo.
Center partition bulkhead flat cars, commonly known as center beam cars, have been known for over 30 years and are depicted, for example, in Taylor U.S. Pat. No. 3,244,120, Wagner U.S. Pat. No. 3,734,031, Baker U.S. Pat. No. 4,543,887, and Saxton U.S. Pat. No. 5,758,584. Evolving design of such railroad cars has been directed generally toward cars with ample strength but of lighter tare weight in comparison to their cargo-carrying capacity. Construction of center beam cars of lighter weight with load-carrying floors located at a uniform height along the length of the car body leaves their load capacity limited by the available space.
Dominguez, et al., U.S. Pat. No. 4,951,575 discloses a center beam car in which a longitudinally intermediate portion of the load-carrying floor on either side of the center beam is located at a lower height than the load-carrying floors located in end portions of the car above the trucks on which the car body is carried. In the intermediate portion of such a car, crossbearers extend between lowered portions of the side sills of the car body and are supported beneath the center sill.
The car disclosed by Dominguez, however, has a conventional box-beam center sill structure, and the crossbearers of the car are attached to the center sill by hanger plates attached to the opposite sides of the center sill and extending downward to support an upper flange portion of each of the crossbearers. The structure of the car shown in the Dominguez et al. patent is thus unnecessarily heavy, making such cars expensive to build and operate.
In most previously available center beam cars the center of gravity has been relatively high because the entire load has been carried above the height of the trucks, but also at least partly as a result of the height of the center partition extending as high as the bulkheads on the ends of the car.
The space above the floor on each side of the center beam forms a bunk upon which bundles of cargo, typically wood products, can be stacked. When the bundles are stacked, they are typically secured by cables or straps that extend from a winch device mounted on the periphery of the floor to a top fitting on the center beam. When the cable or strap is tightened it exerts a force inwardly and downwardly so that the stack leans toward the longitudinal centerline of the car and is pulled tight against the center beam.
The bundles are often wrapped in a plastic sheet to protect the goods from rain and snow, and to discourage embedment of abrasive materials such as sand in valuable goods, such as wood. The plastic sheet typically comprises polyethylene, but may comprise another plastic material.
In previously known center beam cars, various components of the center beam are interconnected in such a manner as to present edges or fastening devices which could rub on the cargo. In addition, when the cables or straps are tightened, the innermost, uppermost elements of the topmost bundle bear against the top chord of the center beam. As the car moves, vibration and inertia cause the stacked cargo to move relative to the center beam. Exposed edges or fastening devices in the center beam structure often abrade, tear, or damage the protective plastic sheeting. Portions of the cargo bearing against the center beam can be physically damaged as a result of contact with exposed edges or projections. Moreover, damaged sheeting may permit entry and collection of moisture and dirt leading to discoloration and the growth of mold on wood products. The resulting loss of value for the cargo can be substantial.
Forbes, U.S. Pat. No. 6,237,506, discloses a smooth, non-consumable panel facing for a portion of the posts of a center beam. The smooth facing protects the plastic sheeting from tearing by reducing exposure to projections and sharp edges on the posts. However, a facing applied to the posts of the center beam does not protect the portion of the sheeting in contact with the top chord of the center beam. Abrasion induced by friction and relative movement of the cargo and the top chord can cause rapid failure of the plastic sheeting exposing the goods to a hostile environment.
What is desired, then, is a center beam or center partition bulkhead flat car defining greater useable cargo-carrying volume and having ample strength yet having lighter tare weight than previously available cars of the type, and in particular including improved center sill and crossbearer structures. What is further desired is a center beam car in which the center beam is constructed so as to be substantially free of edges and projections that can damage the cargo or its containers or coverings and in which the top chord is constructed so as to reduce damage resulting from relative movement of the car and its cargo.